The rail line of a high-speed magnetic train is formed via individual field supports made of steel or concrete. In this case the individual supports themselves can be disposed on level ground or above ground on girders. Flexible steel switches are used so that a moving car can change from one track to another. The switches consist of a steel support of a length of 75 to 150 m, for example, which can be elastically bent with the aid of an electromechanical actuating device. Only individual forces, but no moments, can be transferred to girders of the steel support for generating the bent shape. This means that the bending moment must be linearly limited over the entire length of the steel support and must have a value of zero at the ends of the steel support. It follows from this that the steel support must have a zero curvature at its beginning and end, i.e. a radius of curvature of a. Because of this, a curved steel support has external transitional curved sections in which the radii of curvature increase from oo to a constant value, and a central section following one or several clothoids or an arc of a circle whose radius of curvature corresponds to that of the end sections of the transitional curves. The transitional curves can have a clothoid shape.
A junction often has an undesired length, necessitated by a long elastic line of the elastically bent steel support.